Boosting Oxygen Reduction Reaction Kinetics by Designing Rich Vacancy Coupling Pentagons in the Defective Carbon

Abstract

In the energy conversion context, the design and synthesis of high-performance metal-free carbon nanomaterials with topological defects for the oxygen reduction reaction (ORR) are essential. Herein, we first report a template-assisted strategy to fabricate carbon defect electrocatalysts with rich vacancy coupling pentagons (VP) as active sites in two-dimensional (2D) carbon nanosheets (VP/CNs). Experimental characterizations verify the presence of abundant VP active sites in the VP/CNs electrocatalyst, and the ORR activity is linearly related to the amounts of VP active sites. In situ spectroscopic results identify that the VP/CNs can catalyze direct O–O bond cleavage, bypassing the formation of traditional *OOH intermediates, resulting in the fast kinetics of ORR via a dissociative pathway. The as-prepared VP/CNs show outstanding intrinsic activity for alkaline ORR (half-wave potential of 0.86 V vs reversible hydrogen electrode) with an almost 99% efficiency for four-electron selectivity, outperforming that using the benchmark of Pt/C. Density functional theory calculations further reveal that the cooperative effect between carbon vacancy and adjacent pentagons significantly increases the charge transfer and achieves a lower ORR reaction energy barrier compared with the counterpart of adjacent pentagons or single pentagon. The well-designed carbon defects pave a new avenue for the rational design of metal-free electrocatalysts with high efficiency.

Planar Chlorination Engineering: A Strategy of Completely Breaking the Geometric Symmetry of Fe‐N4 Site for Boosting Oxygen Electroreduction

“…The outstanding ORR activity of Fe-N 4 /CNCl catalyst by planar chlorination engineering of Fe-N 4 site inspires us to further explore its potential application in energy storage devices, such as the Zn-air battery, which is low cost and environmentally friendly with high energy density. [37][38][39][40][41][42][43][44][45] S3, Supporting Information, the Fe-N 4 /CNCl-based Zn-air battery exhibited outstanding catalytic performance during Zn-air battery test, with higher OCV of 1.56 V and peak power density of 228 mW cm −2 . To evaluate the stability of Zn-air battery, the galvanostatic discharge measurement at different current densities were performed, as shown in Figure 4c.…”

Bypassing the scaling relations in oxygen electrocatalysis with geometry-adaptive catalysts

“…While tuning and breaking the OH–OOH scaling relation are well-established in current state-of-the-art, 1,7,34,57–60,66 switching mechanisms represent the cutting edge of research, with confirmed experiments. 62,64,65 To our knowledge, pushing the OH–O/OH scaling relation is computationally conceptualised, 9,61 and awaits experimental verification in direct relation to research on switching. In this work, we propose the geometry adaptation concept as a candidate for the bypassing strategy.…”

Recent Progress and Prospects of Manganese–Nitrogen–Carbon Electrocatalysts for Oxygen Reduction Reaction

“…Template-assisted approaches can enhance the specific surface area of catalysts, optimize pore structure formation, and facilitate exposure and dispersion of active sites, thus boosting the catalytic efficiency and durability of electrochemical reactions. 29,100,126,141,142 The Mn−N x sites typically undergo restructuring during the electrocatalytic ORR process, necessitating further investigation into the impact of coordination configuration and Mn central valence reconstruction. Tong et al 87 engineered Mn single atom sites (Mn-SAS) featuring a consistent and precise Mn−N 4 arrangement.…”

“…The results obtained via DFT were well-aligned with the experimental findings, elucidating additional insights into the effective reactive site of the ORR. Template-assisted approaches can enhance the specific surface area of catalysts, optimize pore structure formation, and facilitate exposure and dispersion of active sites, thus boosting the catalytic efficiency and durability of electrochemical reactions. ,,,, …”